Despite its name, Gamma Knife® isn’t a special, hi-tech, laser-beam surgical knife; it’s a complex machine that delivers finely focused beams of radiation to a single point deep within the brain. Like focused ultrasound, each beam has very little effect on the tissue it passes through. However, a strong dose of radiation is delivered when the individual beams are focused to a single point, destroying the target tissue. The destruction of the target interrupts the signal the brain is sending out telling the muscles to move. Radiosurgical thalamotomy acts as a signal roadblock.
The technique that allows radiosurgery to precisely target the correct area within the brain is called stereotaxy. Several imaging techniques are used together with special computers and instruments, to provide 3-D views of the target area and surrounding brain tissue. Like in DBS, computerized tomography (CT) scanning takes X-ray images from different angles, to produce cross-section images of the brain. This allows the neurosurgeon to see inside the patient’s brain without ever picking up a scalpel. Magnetic resonance imaging (MRI) uses a powerful magnetic field and radio frequency pulses to produce detailed pictures of organs, soft tissues, bone and virtually all other internal body structures. Angiography (x-ray of blood vessels) is also used to ensure the neurosurgeon can even see inside blood vessels and other vital organs. By studying all these images together, a team of specialists can accurately locate the VIM nucleus within the brain, and focus the radiation beams on just that area.
The procedure is not painful. There are no cuts into the scalp or through the skull. However, the neurosurgeon will use local anesthesia to numb four spots on your scalp and forehead before attaching a stereotactic frame. This frame is similar to the one used in DBS and focused ultrasound, and is meant to keep the head immobile and in the correct position during the procedure.
Two-hundred-one highly focused beams of ionizing radiation are generated by activated cobalt. The cobalt beams are directed to converge at the targeted location in the thalamus. The spot where the beams converge is where the tissue destruction occurs. Radiosurgical thalamotomy, similar to focused ultrasound, does not involve putting any foreign objects into the brain. It uses neuroimaging, such as MRI scanning to determine the target location. This procedure takes approximately one hour.
Radiosurgical thalamotomy is an outpatient procedure, so after the procedure, the frame will be removed and you will generally be allowed to go home.
There are early complications or side effects with this procedure, but they are usually temporary. Tiredness and fatigue may occur for the first few weeks. Swelling in the brain at or near the treatment site can cause symptoms such as headache, nausea, and vomiting. The patient’s scalp may be red, irritated, or sensitive at sites where the halo-device was attached to the head during the treatment. Some people also temporarily lose a small amount of hair.
People may also experience late side effects, such as other brain or neurological problems, months after the procedure. In addition, the full benefits of this procedure are often not fully realized until several months post-op.
Radiosurgical thalamotomy is rarely used as a treatment for ET; however, it may be an option in patients that cannot undergo DBS. Significant improvement in tremor has been reported; however, over time, improvement may diminish and additional complications may emerge. Occasionally, patients may require additional surgery if the initial benefits are lost.
Radiosurgery is most commonly used to treat brain tumors, arteriovenous malformations (AVM), and trigeminal neuralgia.
For more information, download the Surgical Options Guide.